Can you translate that for noobs?
What is field supremacy and area control, and why do you need large mounts for that?
What is an extra deadly remote weapon? Or what is a long-range jousting approach?
When has the FdL been "retouched"?
Ok, sorry for having been a bit cryptic.
First, let's get the FdL retouch out of the way. I clearly remember FdL being much less maneuverable than Python, when I last touched it about two years ago. Lateral/vertical thrusters apart, pitch/roll was abysmal, worse than the current Mamba. A Python would have easily outmaneuvered you, and getting a clear aim at an Anaconda power plant was extremely difficult (while it was a piece of cake on a Python). Basically, the FdL was the least maneuverable medium sized ship. As the roll/pitch numbers are now, they make the FdL much better at dogfighting than before; as it outclasses more maneuverable medium ships, as the Federal Assault Ship, in every other compartment, the FdL is now the most capable dogfighter.
Field Supremacy is the ability to see the situation of the battlefield and intervene where necessary. Suppose you're a wing leader; your three wingmen are busy in three dogfights. You want either to 1) help the wingman that can close the fight the fastest, so to achieve numeric superiority as fast as possible, or 2) support the wingman that is suffering the most, in order to prevent the opponent to gain numeric superiority. To do that you need to 1) have a clear picture of the whole battlefield, 2) be able to bring support where needed, and do it fast. The Mamba is the perfect ship to 1) hit hard from afar and 2) bring itself where needed, or 3) disengaging effortlessly where the field needs to be conceded. Even when not in the role of the wingleader, but following orders, the Mamba is the weapon your wingleaders want, in order to bring numerical advantage where they want it, when they want it.
Area Control is a similar concept: it's the idea of creating areas of interdiction for opponents; places where your opponent doesn't want to be. With its speed, the Mamba can use long range weapons to make some areas "poisonous" for the opponent; even if not able to bring a killer DPS from afar, the DPS it can deploy and the ability to hit and run are more than enough to shift the balance of the battle in the area where it's deployed, so that the opponent doesn't want to fight there, or it does, it is likely to lose.
For deadly remote weapon, I meant the large mounts. Large mounts have higher penetration than the medium mounts the FdL has. Being the only medium ship with a huge mount AND two large mounts, it can bring those large hardpoints into a long-range battle as no other medium ship can. The 4 medium on the FdL were a bad customer for sure, but the 2 large on the Mamba are much more dangerous, while its 2 smalls, instead of being a handicap, can be used for utility (i.e. to apply debufs) while absorbing less power than medium hardpoints used for that purpose on the FdL.
As for the long range Jousting, it's a variant of Jousting. There are different fighting techniques in this game, and you have to pick the right one for the situation at hand, and for the ships involved in the fight. Jousting is flying at relatively high speed towards the opponent, firing when approaching, turning around and repeating. It usually takes two to tango, unless you are MUCH faster than your opponent, in which case you can joust alone on a quasi-static target. The idea of jousting is that both of the opponents are betting on who has the highest DPS/shield-armor ratio, and can turn its hardpoint on target faster; the one that got its estimation right wins (or in case much faster than your opponent, you're the only one betting on your DPS/shielding ratio and hardpoint positioning, forcing your opponent to accept your bet and hope you're wrong).
Long-range Jousting is like jousting, but with the ability to grind at the opponent defense from afar added in the picture. For example, firing long-range engineered beam lasers, then discharging short range, higher damage-per-hit weapons (frag cannons, cannons, plasma accelerators) when getting near, passing by your opponent and repeating.
While you just need a good DPS/shield-armor ratio to joust, to do long-range jousting you need also speed: you want change your long-range/short-range positioning as fast as possible. FdL was good at that, but not perfect; for this technique, Mamba is the real deal.
In short, Mamba has a very specific role and a very specific preferential fighting technique in which it excels. But it has also something more: it can determine the rhythm of the battle.
In a dogfight against an equally equipped FdL and an equally skilled pilot, Mamba is sure to lose, but the Mamba doesn't have to accept the fight on the FdL terms. Other than the supremacy/control roles we talked above, at the moment, the Mamba is the only ship that can say: "you're either fighting on my terms, or I am not fighting" -- and that's an immense advantage. Its only preferential fighting technique is long range Jousting, and it kinda suck at everything else, but it's the only ship that can say "we're either long-range jousting, where I am the best, or I am out of here".
As a PvP generic fighter ship, I think the FdL is superior; but there are some roles that the Mamba covers much better, and I happen to like them. So, the Mamba might be for you, if you prefer a more tactical, high-level play style. (Also, the introduction of the Mamba allowed the FdL to focus on its preferential role, so that it doesn't have to spread thin on field supremacy and area control, where it was good, but less than optimal).